As a display device for displaying the above described display level, it is known that, for example, a liquid crystal indicator is used to display a bar graph. The liquid crystal indicator is capable of displaying the bar graph with good appearance, but the cost is high. Therefore, as shown in FIG. 10, a display device is provided that uses a plurality of LEDs to display a bar graph (for example, Patent Literatures 1 and 2).
As shown by (B) in FIG. 10, the display device 1 includes a first LED group 2 (a group of first light emitting elements), a display panel 10 and a casing 4. The first LED group 2 includes a plurality of LEDs 21 to 25 (the first light emitting elements) arranged in a line on a substrate 6. Light emission of the LEDs 21 to 25 is controlled by a microcomputer not shown in the figure. The display panel 10 is arranged at the front side of the plurality of LEDs 21 to 25, and a plurality of segmented bars 11 to 15 (referring to (A) in FIG. 10) having light transmission property are arranged on the display panel 10 opposite to the respective LEDs 21 to 25. The casing 4 is arranged between the display panel 10 and the LEDs 21 to 25, and shaped into a quadrangle barrel which has openings to its front and rear sides.
Next, the behavior of the display device 1 with the above described structure will be explained below. For example, when a display level “3” is to be displayed, the microcomputer 5 makes some LEDs in the first LED group 2, that are from the LED 21 at the left end in the arrangement direction of the first LED group 2 to the LED 23 at a position corresponding to the display level “3” (the third one from the left) to emit light, as shown by (B) in FIG. 10. The light from these LEDs 21 to 23 passes through the corresponding segmented bars 11 to 13 and is emitted to the front side. In this way, as shown by (A) in FIG. 10, the segmented bars 11 to 13 from the leftmost one to the third one are lighted on and thus can be visually recognized, therefore enabling to indicate the display level.
However, the above described LED display device has a problem of lacking design properties as compared with a liquid crystal indicator. In addition, when the display level to be displayed changes in a short time from “2” to “3”, from “3” to “2” or the like, as shown in FIG. 11, the segmented bar 13 corresponding to the display level “3” is turned on, and immediately turned off again, thus resulting in a problem of flickering.